Microfluidics is a low-cost technique for fast-diagnosis and micro-synthesis. Within a decade it might become the foundation of Point-of-Care (POC) and Lab-on-a-Chip (LOC) applications. In microfluidic research, control of micro-droplets is one of the basic topics. Those pico-liter droplets are perfectly suitable for micro-synthesis, drug screening, and chemical tracing. As a result, large-scale integration and high-density control unions are required. Meanwhile, individual manipulation of micro-droplets remains a challenge: the shortcomings in automatic, reliable and scalable methods for logic control prevent further integration of microfluidic applications. simple control schemes are required while preserving the delicacy of micro-devices....[ Read more ]

Microfluidics is a low-cost technique for fast-diagnosis and micro-synthesis. Within a decade it might become the foundation of Point-of-Care (POC) and Lab-on-a-Chip (LOC) applications. In microfluidic research, control of micro-droplets is one of the basic topics. Those pico-liter droplets are perfectly suitable for micro-synthesis, drug screening, and chemical tracing. As a result, large-scale integration and high-density control unions are required. Meanwhile, individual manipulation of micro-droplets remains a challenge: the shortcomings in automatic, reliable and scalable methods for logic control prevent further integration of microfluidic applications. simple control schemes are required while preserving the delicacy of micro-devices.

Among the materials that used for microfluidic chip fabrication, Polydimethylsiloxane (PDMS) is one of the most commonly used, not only serving as the stamp for pattern transfer, but also as an unique substrate in chip fabrication owing to its properties such as transparency, biocompatibility, and good flexibility. By employing PDMS, various chip-embedded control modules are realized. However, PDMS is a non-conducting polymer, on which fabricating metallic structures for micro-devices is challenging due to the weak adhesion between the metal and PDMS. Therefore, transport of electric signal is one of the fundamental difficulties to realize digitalized control on PDMS based microfluidic chip, which restricted further development of LOC and POC applications.

This thesis presents two approaches to realize digitalized control of microfluid chips. One is to develop functional material, which is CI-PDMS that responds to electric and magnetic field. CI-PDMS is a kind of magnetic elastomer that is fabricated out of PDMS and nano powder. Another approach is to develop micro microstructures and components that provide active control and digitalized response in PDMS based chips. We employed CI-PDMS, AgPDMS and Giant Electrorheological Fluid (GERF), which are smart material that incorporate nano structures, to fabricated micro-pressure sensors, micro-actuators, micro-mixers and micro-logic gate, to convey the electrical signals, and perform chip operation in digitalized approach. We realized the first microfluid based universal logic gate by incorporating the smart material developed in our lab, and provided a facile structure to implement the microfluid logic control by this new logic component. We further proposed a simple and fast chip prototyping method, which is time saving and cost effective to fabricate the microstructure developed in our lab, as an improvement of existing microfluidic chip fabrication technology. In the final part, a summary of these interwoven technologies is presented in the form of technology family tree, while a prospect is provided for the future development of the trend of digitalized microfluidics.